The present invention relates in general to visual devices for indicating rotation of machine elements normally shielded from direct view by a user. More particularly, the invention is directed to a luminous indicator device that is electrically powered solely by energy derived from the rotating element which the indicator is monitoring. The invention can be used, for example, to provide a self-powered rotation indicator that is mounted within a detachable rug cleaning nozzle of a domestic vacuum cleaner wherein rotation of a beater brush within the nozzle is indicated by illumination of a portion of the indicator viewable by a user.
It is known in the art to provide light-emitting devices for indicating rotation of elements shielded from direct view by a user. U.S. Pat. No. 4,245,370 to Baker discloses such a device.
In the prior art Baker device, a magnet is carried by a rotating beater brush housed within the rug cleaning nozzle of a domestic vacuum cleaner. The magnet revolves about the axis of rotation of the beater brush as it rotates. A Hall effect sensor located adjacent to the path of the revolving magnet provides a pulse signal whose frequency is indicative of the rotational speed of the beater brush. This sensor signal is inputted to a relatively complex, externally-powered, control circuit that performs various functions including illumination of a selected one of a plurality of user viewable light-emitting diodes that indicate the rotational status of the beater brush.
While the prior art Baker device functions to provide a visual indication of the rotational status of a concealed member, i.e. a rug beater brush, its complexity makes it unattractive from a cost and reliability standpoint. There is a need for a rugged and highly reliable rotation indicator that would be self-powered and very low in cost so that it could be easily mounted and wholly contained within a detachable rug cleaning nozzle of a domestic vacuum cleaner, it being recognized that the domestic appliance business is highly competitive.